The invention starts out from a method according to the preamble of the main claim. Such a method is known from WO 03/012577 A3. There a method is described for automatically installing a function unit on a host computer equipped to recognize certain mass memory units. According to the method the function unit to be installed first registers with the host computer as a standard mass memory. For this purpose it is provided with an emulator that can be switched off and which is switched on in the initially preset basic mode. After registering as a mass memory the function unit induces the host computer to communicate a data sequence containing information about whether the drivers and configuration means corresponding to the function unit are present on the host computer. If this is not the case, the function unit further induces the host computer to provide it with information about the operating system installed on the host computer. In accordance with the thus determined operating system the function unit selects suitable drivers and configuration means among several such drivers and configuration means stored on the function unit and transmits them to the host computer. After installing the transmitted drivers and configuration means the function unit is switched to a function-unit specific operating mode and the installation is concluded.
The known method permits the installation of a function unit on a host computer which is not prepared for the function unit at first and does not have the drivers and configuration means required for operating the function unit. However, it implies that the function unit acts at least partly as an active component towards the host computer during the installation phase. Therefore the method is not suitable for arrangements designed strictly according to the “master-slave principle”, in which the host computer acts exclusively as master. The transmission of information about the host computer to the function unit for the purpose of selecting the drivers is furthermore difficult to implement. Such a transmission can be simulated by a user by simulating manual input. However, this bears the risk that errors occur in user inputs during the installation phase.
From WO 2004/008313 A1 a method is known for establishing cooperation between a host computer and a function unit carrying out a sub-function within the framework of an application run on the host computer. In order to introduce the sub-functions provided on the function unit to the host computer, the function unit first registers in a first configuration as a standard mass memory and transmits information about supported standard applications to the host computer. One of the standard applications is designed to determine the further sub-functions provided on the function unit. Furthermore, the host computer communicates the operating system used to the function unit. On the basis of the information the function unit determines the sub-functions to be activated for the possible applications and the operating routines required on the host computer for the execution thereof. Subsequently the function unit is restarted. It now registers with the host computer with an enhanced, second configuration comprising the standard functions and in addition the now activated sub-functions. Furthermore the required operating routines are transmitted to the host computer. The auxiliary unit is switched from the first to the second configuration with the aid of a flag. A fast implementation of the method, in particular, as proposed, for USB smart cards, conflicts with the fact that the proposed determination of the available sub-functions by a standard application and likewise the communication of the operating system used cannot be reconciled easily with the USB standard. Moreover, registering the auxiliary unit in a composite configuration bears the risk that a host computer accepts only the first formally indicated one.